INFLUENCE OF GIBBERELLIN BIOSYNTHESIS INHIBITORS ON STEM ELONGATION AND FLORAL INITIATION ON IN-VITRO CHICORY ROOT EXPLANTS UNDER DARK AND LIGHT CONDITIONS

Root explants of chicory (Cichorium intybus L.) were cultured in vitro under continuous light or darkness. On a standard medium (no plant growth regulators added), flowering-stems were initiated under continuous light while under continuous dark, vegetative-stems were formed. Different types of GA (gibberellin) biosynthesis inhibitors were added to the culture medium. Paclobutrazol and compounds belonging to the group of cyclohexanetriones clearly reduced flowering-stem growth under light conditions and vegetative-stem growth under dark conditions. Under light conditions, flower bud initiation was not affected. These and other results suggest that GA(1) may be synthesized during the in vitro culture period and that it controls flowering-stem growth but not floral initiation.